Thin plastic film

Abstract

A covering for a portion of a body or an object, as well as improved, thin plastic films for use in such coverings, are disclosed. The covering comprises a thin plastic film and a pressure sensitive adhesive contacting at least a portion of, and forming a joint with, the thin plastic film. The plastic film comprises from about 85 to about 95 weight percent plastic, and from about 5 to about 15 weight percent tackifier. Such joints may be found in diapers, adult incontinent briefs, bandages, and other body coverings, as well as packagings for a variety of objects. Such joints exhibit unexpectedly high shear adhesion as compared to conventional joints.

Description

The present invention generally relates to thin plastic films and, more particularly, but not by way of limitation, to an improved joint between a thin plastic film and a pressure sensitive adhesive.HISTORY OF THE RELATED ARTThin plastic films are used in a variety of consumer products. Some typical applications include body coverings such as baby diapers, adult incontinent briefs, and bandages, as well as packagings for a variety of other products. In each of these applications, a joint between the thin plastic film and a pressure sensitive adhesive may be required.FIGS. 1 and 2 show schematic views of a conventional diaper 10. Referring first to FIG. 1, diaper 10 has a backsheet 12 formed from a thin plastic film. Backsheet 12 is formed into a "T-shape" so that tee extensions or tee tabs 14 can be used like a belt or strap for fastening diaper 10 around a baby. A landing zone 16 is located on the opposite end of backsheet 12 from tee tabs 14. Diaper tapes 17 are adhered to backshe...

AI Technical Summary

Benefits of technology

The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. For example, numerous geometries, including the above-described geometries of the joints formed between the improved films of the present invention and a pressure sensitive adhesive, could be altered. As another example, although the present invention has been described in connection with baby diapers, incontinent briefs, bandages, and applying pressure sensitive adhesive labels to plastic film packagings, the improved films of the present invention are fully applicable to other, similar products, including, without limitation, other body coverings where a pressure sensitive adhesive joint with a plastic film is contemplated. Such body coverings may include medical drapes, medical gowns, medical smocks, ostomy appliances, feminine hygiene products, body transfer sheets, fluid collection pouches, or industrial clean room garments.

Problems solved by technology

However, these joints are subject to certain limitations.

For example, when the plastic films, and / or the joints formed between the plastic films and the pressure sensitive adhesives, are subjected to high ambient temperature conditions for an extended period of time, such as during storage in a warehouse in a hot climate, the strength of such joints is adversely affected.

In addition, when such plastic films are formed with a rough surface, such as, by way of example, embossing a large scale pattern on the film, or forming apertures or holes in the film, the strength of a joint formed using such film is adversely affected.

However, it is often difficult to find, or cost-prohibitive to use, a commercially available pressure sensitive adhesive that has the necessary adhesive properties to form such joints.

Furthermore, higher strength adhesives may not be applicable in bandage 50 where the adhesive contacts the user's skin.

However, the beneficial surface activation achieved by corona treatment decreases quickly with time at high ambient temperatures.

However, these techniques require expensive and physically large equipment and involve dangerous substances or sources of combustion.

Failure almost always occurs in a creep mode.

However, when the control film formed with a large scale rough surface was subjected to the HASHT test, the sample failed after about 60 minutes, substantially below the desired HASHT of about 500 minutes.

However, when the films have a large scale, rough surface, and particularly when such joints are subjected to high ambient temperatures, such as 120.degree. F., for several days, the joints fail under shear in an unacceptably short time frame.

These tackifier concentrates are formed because most pure tackifiers melt prematurely on the extruder screw of conventional film extruders due to their low melting point.

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